4-vinyl pyridine polymers of improved properties for purification of polymers containing ziegler-nata catalyst residues

ABSTRACT

A 4-VINYL PYRIDINE COPOLYMER OR TERPOLYMER USEFUL IN THE PURIFICATION OF POLYMERS PREPARED BY IONIC POLYMERIZATION, E.G. WITH ZIEGLER-NATA CATALYSTS; THE COPOLYMERS AND TERPOLYMERS OF SAID 4-VINYL PYRIDINE ARE PREPARED BY COPOLYMERIZING 4-VINYL PYRIDINE WITH DIVINYL BENZENE, AND STYRENE FOR THE TERPOLYMER, IN A SPECIFIC RATIO OF MONOMERS TO SOLVENT TO OBTAIN A COPLOYMER OR TERPOLYMER WITH A DEFINED AND IMPROVED ACCESSIBLITY OF THE NITROGEN ATOM TO THE IMPURITIES IN THE POLYMERS SOUGHT TO BE PURIFIED; INCLUDED WITHIN THE INVENTION ARE THE METHOD FOR PREPARING AND THE METHOD FOR UTILIZING SAID COPOLYMERS AND TERPOLYMERS OF SAID 4-VINYL PYRIDINE.

United States Patent 3,718,631 4-VINYL PYRIDINE POLYMERS OF IMPROVED PROPERTIES FOR PURIFICATION OF POLY- MERS CONTAINING ZIEGLER-NATA CATA- LYST RESIDUES Jacques Grosmangin and Jean Peyrot, Le Havre, France, assignors to Compagnie Francaise de Raflinage, Paris, France No Drawing. Filed Nov. 16, 1970, Ser. No. 90,102 Claims priority, application France, Nov. 15, 1969, 6939352 Int. Cl. C08f /00 US. Cl. 260-80.72 13 Claims ABSTRACT OF THE DISCLOSURE A 4-vinyl pyridine copolymer or terpolymer useful in the purification of polymers prepared by ionic polymerization, e.g. with Ziegler-Nata catalysts; the copolymers and terpolymers of said 4-vinyl pyridine are prepared by copolymerizing 4-vinyl pyridine with divinyl benzene, and styrene for the terpolymer, in a specific ratio of monomers to solvent to obtain a copolymer or terpol mer with a defined and improved accessibility of the nitrogen atom to the impurities in the polymers sought to be purified; included within the invention are the method for preparing and the method for utilizing said copolymers and terpolymers of said 4-vinyl pyridine.

The present invention relates to resins containing poly- 4-vinyl pyridine and the method of manufacturing these resins.

It also concerns the application of the said resins to the purification of polymers in solution.

In the present specification, the expressions basic copolymers or resins refer to copolymers which contain heterogeneous atoms (that is to say, which are neither carbon atoms nor hydrogen atoms) having electron doublets not contained in bonds and which therefore have a basic function in accordance with Lewis definition. By the word polymers there shall be designated all other polymers and in particular polymers which have only carbon and hydrogen atoms. The expression active atoms will be used to designate heterogeneous atoms which have at least one doublet of electrons not contained in bonds.

The applicants assignee in prior patent applications (e.g., Ser. No. 691,138, filed Dec. 18, 1967 refile'd as a continuation-in-part application Ser. No. 50,977 filed June 29, 1970, and now abandoned and refiled as continuation application Ser. No. 252,279 filed May 11, 1972, and based in part on French application No. PV 88,204 filed Dec. 20, 1966 and in part on French application No. PV 130,976 filed Dec. 5, 1967) has already described a method of purifying polymers obtained by ionic polymerization, particularly in the presence of catalysts of the Ziegler-Natta type. One such method consists in contacting the solution of the said polymers with a basic copolymer, separating the solution and the basic copolymer after the latter has retained the soluble components of the catalytic system (which have an acid function within the definition of Lewis and are harmful to the properties of the polymers), regenerating the said basic copolymer, and finally contacting it with a new solution of polymers to be purified.

For the carrying out of this process, the basic copolymer must have special properties: it must withstand hot solvents, have a satisfactory particle size and have a good resistance to erosion and swelling; finally, the active atoms must be easily accessible to the metallic elements to be eliminated.

3,718,631 Patented Feb. 27, 1973 An object of the present invention is the production of resins consisting of basic copolymers having improved accessibility of the active atoms as compared with the known resins, the accessibility of which does not exceed 20%. In these known resins, less than one-quarter of the active atoms (nitrogen, for example) are involved in the process of complexing of the metallic elements to be eliminated from the solutions of polymers.

During this work on the purification of polymers, the applicants have found that the accessibility of the active atoms depended on the porosity of the resins serving for the purification. This accessibility increases with the porosity. It is necessary to distinguish between two types of porosity: permanent porosity which is related to the specific surface of the resin and the porosity of swelling which manifests itself only when the resin is in the presence of a swelling agent.

The invention concerns a resin composed of a copolymer of 4-vinyl pyridine and divinyl benzene, and in a further embodiment may additionally incorporate styrene, in accordance with respective contents, expressed in weight referred to the resin, of between 30% and 70%, 10% and 60%, and 0% and 40%, the said copolymer being characterized by the fact that it has an accessibility of the nitrogen atoms of more than 50% The accessibility of the nitrogen atoms is measured by contacting the resin with a solution of a transition metal salt, for instance titanium tetrachloride TiCl It is expressed by the number of molecules of the transition metal salt which have fixed themselves on the resin per atoms of nitrogen contained in said resin.

Another aspect of the invention is a method of manufacturing resins which are formed of copolymers of 4- vinyl pyridine, divinyl benzene and possibly also styrene, the accessibility of the nitrogen atoms of which is greater than 50%. The method is characterized by the fact that the copolymerization reaction is carried out in an inert gas atmosphere, at a temperature of between 60 C. and C., and in the presence of a solvent for the monomers involved which solvent can also dissolve each of the homopolymers of said respective monomers separately, or of precipitating them. This method further utilizes a volume of solvent such that the ratio of the volume of the monomers to the sum of the volumes of the monomers and of the solvent is between 0.2 and 0.6; and also utilizes a quantity of divinyl benzene in the reaction medium of between 10% and 60% by weight of the mixture of monomers introduced and a quantity of styrene in the mixture of between 0% and 40% by weight of the mixture of monomers.

Another aspect of the invention concerns a process of removing from solutions of polymers traces of metallic elements which they contain when said polymers have been formed in the course of ionic reactions, particularly in the presence of Ziegler-Natta catalysts, Where the resins produced in accordance with the present invention are used.

Depending on Whether the resins of the invention contain styrene or not, one distinguishes between two types namely:

(1) Resins whose formula does not contain styrene have only permanent porosity;

(2) Resins whose formula contains styrene may either have permanent porosity or exhibit a swelling porosity in the presence of a given agent, or have both types of porosity simultaneously.

Permanent porosity is dependent only on the manner of manufacture of the resin, and in particular, on the amounts of divinyl benzene, or divinyl benzene plus styrene, introduced into the reaction medium, as well as the relative volumes of solvent and monomers in the medium.

The swelling porosity depends only on the swelling agent in the presence of which the resin is used, it being understood that the latter contains recurrent styrene units. Xylene, for instance, is a swelling agent.

As has been indicated above, the solvent for the monotion a temperature close to 80 C., for instance, in a nitrogen atmosphere for a period of time which may vary between 30 minutes and several hours. This period of time is not critical. Thereupon the resin is preferably filtered and then washed with water and finally extracted r a e e a a mers should either be a solvent for each of the separate for a few hours 1n a n1trogen atmosphere with pyridine homopolymers thereof taken separately, or should prebefore being carefully dried. cipitate each of these homopolymers taken separately. The resin obtained by this method can then be used This is an important characteristic of the invention, since in a stationary bed or in a fluid or moving bed for the one does not obtain resins of high accessibility if one purification of polymers when ionic catalysts such as the effects the copolymerization in the presence of a solvent Ziegler-Nata catalysts have been used in their prepwhich would dissolve one of the homopolymers and not aration. the other. This would be true of toluene making it un- The purification of the polymers is effected in a solvent acceptable for use in this invention. The solvent is theremedium which differs according to whether the resin fore selected in accordance with this criterion;which does has a permanent porosity or, if it has been prepared not, however, mean that homopolymers are present in with styrene, to whether it has a swelling porosity. In the reaction meduim. the latter case in order to benefit from the swelling Where one wishes to operate in the presence of a solporosity, it is necessary to operate in a suitable solvent vent for the monomers and homopolymers, one can use, which is both a swelling agent for the resin and a solvent for example, pyridine, since it is a common solvent for for the polymers to be purified. poly-4-vinyl pyridine, polyvinyl benzene and polystyrene. The polymer purification operation is carried out in The saturated hydrocarbons, for instance heptane, are the manner described in the aforementioned preceding solvents for monomers which precipitate homopolymers patent application. This consists of contacting the purifyof 4-vinyl pyridine, divinyl benzene and polystyrene, reing resin with the dissolved, or (if necessary) liquified spectively. They could therefore be used to carry out the polymers-to-be-purified. When a resin of swelling porosity process of the invention. is used, then one must treat the dissolved polymers in a Applicants have established that the copolymerization solvent which is also a swelling agent for the resin. Such reaction takes place under favorable conditions if the a solvent, for instance, consists of aromatic hydrocarbons, reaction medium, i.e., the monomers and the solvent, are and particularly xylene. dispersed. Thus, in accordance with a preferred embodi- 0 All the tests carried out by the applicants utilizing ment of the process of the invention, the reaction medium resins according to the present invention in the purificais dispersed in water. The reaction medium is thus placed tion of polymers have established that less resin is rein suspension. The word suspension being given here quired to purify a given mass of polymers than was necesmerely by way of indication, without being, however, sary previously, apparently as a result of the improved limited by the precise physical meaning of this term. accessibility of these resins. In addition to this economic A typical copolymerization mixture comprises 4-vinyl advantage, a technical advantage is also obtained. For pyridine and divinyl benzene dissolved in a solvent and a given mass of polymers, the bed of resin will be thinner dispersed in water to which polyvinyl alcohol has been and therefore the loss in head necessarily suffered by the added. It is advantageous also to add azo-bis-isobutyrofluid medium which passes through the resin bed will be nitrile which is intended to initiate the copolymerization less than that which it suffers with a resin of conventional reaction. When pyridine is used as solvent for the polymtype. erization medium, sodium chloride is added to the water f0l10WlT 1g Examples which not of a 'llmltaflve in order to prevent the Pyridine fr dissolving, since character provide a practical illustration of the invention, it is partially soluble in water. The reaction medium is with reference to Table I belowmaintained in suspension by agitating the mixture of water, polyvinyl alcohol and solution of monomers in EXAMPLES I to VII the Solvent By application of the invention there were synthesized As the p y y alcohol serves as dispersant in h seven lots of resin, I to VII, which were prepared with mixture, it is obvious that this alcohol can be replaced ditferent proportions of reagents as set forth in Table I.

TABLE I I II III IV v VI VII Production of the resins:

Divinyl benzene (at in cc 20 25 10 10 20 30 M 4-vinyl pyridine in ce 15 10 25 25 25 25 15 Styrene in cc 15 15 15 15 10 Azo-bis-isobutyronitrile in g. 1 1 1 1 1 1 1 Solvent:

Heptane cc.; Fm 50; 0. 5 200; 0 2 Pyridine 00.; Fm 52. 5; 0.4 52.5; 0 4 100; 0.38 100; 0.41 0.41 Water, in co 130 130 130 Sodium chloride in g 18 18 18 18 18 Polyvinyl alcohol in g 2 2 2 2 2 2 Properties of the resins:

Specific surface in rnJ/g 194 235 78 120 TiClt fixing medium:

(a) Heptane-. Yes Yes Yes Yes (b) Xylene Yes Yes Yes Fixing in millimols 3.5 2. 9 4. 0 5 4 3. 5 a. 2 Accessibility of nitrogen atoms in percent. 80 80 100 100 100 by any other product having the same dispersing func- These reagents are vinyl pyridine, divinyl benzene (in tion. Likewise, the azo-bis-isobutyronitrile intended to the specific case commercial divinyl benzene of a density initiate the radical reaction can be replaced by another of 0.9 and containing 55% pure divinyl benzene); the radical initiator; benzoyl peroxide, for instance. 70 solvent of the copolymerization medium is either pyridine In the event that a saturated hydrocarbon insoluble in water is used as solvent for the copolymerization medium, it is not necessary to add salt to avoid partial solubilizing of the solvent in the water.

when one operates in the presence of a solvent for the homopolymers (considered separately), or heptane in the event that one uses a solvent for the monomers which is a precipitant of the homopolymers (considered separate- The copolymerization reaction is carried out with agita- 75 1y).

Finally, azo-bis-isobutyronitrile is used to initiate the reaction.

The products together constitute the reaction medium.

In the table, F designates the value of the ratio of the volume of the monomers to the sum of the volume of the monomers and the volume of the solvent.

This reaction medium is introduced slowly into a 2- liter reactor which is provided with an agitator and contains water and polyvinyl alcohol as dispersing agent. Sodium chloride is added to this medium when pyridine is used in order to prevent the latter from dissolving in the water.

The different synthesis reactions are carried out in a nitrogen atmosphere with agitation for 6 hours at a temperature of 80 C. Each of the lots of resins is then filtered, washed with water, then extracted for 8 hours in a nitrogen atmosphere with pyridine and finally dried in vacuum for 12 hours at 80 C.

In Table I there are entered the various proportions of the reagents entering into the synthesis medium, as well as the composition of the medium in which this synthesis medium is dispersed.

This table also indicates the characteristics of the different resins obtained and their accessibility expressed in percent (percent) of the accessible nitrogen atoms.

In this table, TiCL; fixing medium designates the solvent in which the titanium tetrachloride is dissolved in order to cause it to pass onto the resin so as to test the accessibility of the nitrogen atoms of said resin.

From these examples it is seen that the resins prepared in accordance with the invention all have an accessibility which is at least equal to 80%. It is also seen, upon comparing Examples III and IV with the other examples that although the quantity of divinyl benzene present is very small, one can obtain a high accessibility of the nitrogen atoms by compensating for the small proportion of divinyl benzene with'styrene and effecting the fixing of the titanium tetrachloride in a swelling medium such as xylene.

EXAMPLE VIII This example illustrates the purification of a polymer in solution by passage over a column packed with a resin in accordance with the invention and operating in a nitrogen atmosphere.

A resin in accordance with the invention of a particle size of between 250 and 990, and the accessibility of the nitrogen atoms of which is equalto 100 is introduced into a column of a cross-section of 47.8 cm. over a height of 56 cm.

A solution of polybutene of 8 g./l. in xylene is passed through the column. The rate of flow of the solution is fixed at 1.5 l./hr.; the temperatures of the column and of the solution are maintained at 120 C.

Table II below shows the purification of the solution obtained by passage through the column. It will be noted that the initial polybutene solution has a very high content of catalytic residues. Columns 2 and 3 of this table indicate the concentrations of'the solution in metallic elements before and after passage through the column respectively.

TABLE II Concentration of elements in the solution (p.p.m.)

We claim: 1. A resin of a copolymer or terpolymer consisting essentially of 4-vinyl pyridine and divinyl benzene or 4-vinyl pyridine, divinyl benzene and styrene in the amounts expressed in weight referred to the resin between 30% to 70%, 10% to 60%, and 0% to 40%, respectively, said copolymer or terpolymer having an accessibility of nitrogen atoms of more than 50% defined as the ratio in percent of the number of molecules of TiCl which have fixed themselves on the copolymer or terpolymer per atoms of nitrogen contained in said resin when contacting said resin with a solution of said TiCl 2. A resin as claimed in claim 1 wherein said amounts are 40% to 70%, 30% to 60%, and 0%, respectively.

3. In a method for manufacturing resins formed of copolymers or terpolymers of the monomers 4-vinyl pyridine, divinyl benzene and styrene, the accessibility of the nitrogen atoms of which copolymers or terpolymers is greater than 50% defined as the ratio in percent of the number of molecules of TiCl which have fixed themselves on the copolymer or terpolymer per 100 atoms of nitrogen contained in said resin when contacting said resin with a solution of said TiCl the improvement which comprises dispersing said monomers in water in presence of a solvent for said monomers, carrying out the copolymerization reaction in an inert gas atmosphere at a temperature of between 60 C. and C. in the presence of a said solvent for the monomers, said solvent being capable either of dissolving each of homopolymers formed from said monomers separately or of precipitating them separately, the volume of said solvent being such that the ratio of the volume of the monomers to the sum of the volume of the monomers plus that of the solvent is between 0.2 and 0.6; the quantities of 4- vinyl pyridine, divinyl benzene and styrene introduced into the reaction medium being within the ranges of 30% to 70%, 10% to 60% and 0% to 40% by weight, respectively, of the mixture of monomers introduced, said solvent being selected from the group consisting of pyridine, and a liquid, saturated hydrocarbon including a dispersing agent and a radical initiator for said polymer and agitating a mixture of said monomers, solvent, water, dispersing agent and initiator.

4. The method according to claim 3 wherein the mixture includes pyridine as solvent and sodium chloride as additive to avoid the solubilizing of the solvent in water.

5. A method according to claim 3 wherein the solvent is a liquid saturated hydrocarbon in which styrene is introduced in said mixture and said terpolymer has up to 40% styrene by weight therein.

6. A method according to claim 3 wherein the solvent is heptane.

7. A method according to claim 3 wherein said radical initiator is azo-bis-isobutyronitrile.

8. A method according to claim 3 wherein said radical initiator is benzoyl peroxide.

9. A method according to claim 3 wherein said dispersing agent is polyvinyl alcohol.

10. In a method for purifying polymers obtained by ionic polymerization whereby said polymers contain residues of a catalyst and whereby a copolymer or terpolymer of 4-vinyl pyridine is used as means to purify said polymer, the improvement comprising contacting in an inert gas atmosphere a solution of polymer sought to be purified with a copolymer consisting essentially of 4-vinyl pyridine and divinyl benzene or a terpolymer consisting essentially of 4-vinyl pyridine, divinyl benzene and styrene in the amounts expressed in weight referred to the copolymer or terpolymer between 30% to 70%, 10%. to 60%, and 0% to 40%, respectively, said copolymer or terpolymer having an accessibility of nitrogen atoms of more than 50% defined as the ratio in percent of the number of molecules of TiCl which have fixed themselves on the copolymer or terpolymer per 100 atoms of nitrogen contained in said resin when contacting said resin with a solution of said TiCL; and separating the solution of said polymer thus purified from said copolymer or terpolymer of said 4-vinyl pyridine.

11. The method according to claim 10 wherein the polymer to be purified is in solution in a swelling agent for the 4-vinyl pyridine terpolymer.

12. The method according to claim 11 wherein the swelling agent is an aromatic hydrocarbon.

13. The method according to claim 11 wherein the swelling agent is xylene.

References Cited UNITED STATES PATENTS 2,540,984 2/1951 Jackson 260-88.l 2,732,351 1/1956 Clarke 2602.l

8 2,828,270 3/1958 Murata 2602.1 3,410,838 11/1968 Strobel 260--94.7 3,553,180 1/1971 Cleary 2608().72

' FOREIGN PATENTS 1,519,614 4/1968 France 260--94.9

JOSEPH L. SCI-IOFER, Primary Examiner S. M. LEVIN, Assistant Examiner US. Cl. X.R.

26033.6 R, 33.6 PQ, 88.1 PA, 94.9 F 

